dhcp relay agent and secondary addrss issues

[zhangyb]

when i config " ip helper-address ..." command, the router can take the role of

dhcp relay agent. but if the interface has two ip addresses configued,what i need know is that, when routers forward dhcp discovery packets, which address will be used as the relay agent address (giaddr), primary or secondary address, even randomly

selected ?

my platform are cat6509 and cat2948g, i actually need primary address be

giaddr address. if cisco devices set the giaddr address randomly, is there some commands configued to force routers use primary or seconday address ? or ,is this related to ios version?

i know there is command " cable dhcp-giaddr policy" on CMTS, is there something like this on routers and switch platform?

[bradwong]

The router should always use the primary address to populate the giaddr field of the DHCP request.

[zhangyb]

thanks for your reply.

[paumercier]

The router will always use the primary address. If you are attempting to expand the available dhcp scope with the use of secondary addressing you will need to search for dhcp servers that support this type of behavior. --- Some DHCP servers (QIP) now accomadate the use of secondaries by tagging (within the servers dhcp service) a secondary scope that will provide additional IPs in the secondary range if the primary range is exhausted. Not the best way to solve the problem (should supernet) but works if you have no other method or provide time to reconfigure network to allow larger dhcp scope. Not aware of other dhcp servers that allow this but I'll bet QIP isn't the only implementation.